Flow rate compensator



May 24, 1960 F. P. EVANS ETAL 2,937,656

FLOW RATE COMPENSATOR Filed Aug. 26, 1958 3 Sheets-Sheet l /4 M F/G. A H 2% i i M w 1'T 4X 1 A 764907725 VflZVE P007770 INVENTOPS FRED/PICK EVANS RICHARD K. MASON By W m 14/ MM ATTORNEY May 24, 1960 F. P. EVANS EI'AL Y 2,937,656

FLOW RATE COMPENSATOR Filed Aug. 26, 1958 3 Sheets-Sheet 2 THE 7 5 0 PC Z v INVE/V TOPS FPEDRICK I? EVANS RICHARD K. MASON 8V MA r: M

A T TOPNE) May 24, 1960 F. P. EVANS ETAL 2,937,656

FLOW RATE COMPENSATOR IN VE'N TOPS FRED/PICK R E VANS RICHARD Ir. MASON By X91470?) A/MM A TTO/PNE) United States Patent() FLOW RATE COMPENSATOR Fredrick P. Evans, Longmeadow, Mass., and Richard K. Mason, Windsor, Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Aug. 26, 1958, Ser. No. 757,305

8 Claims. (Cl. 137-110) This invention relates to fluid control systems and more particularly to throttle valves used therein to control the rate of controlled fluid flow therethrough.

It is an object of this invention to teach a fluid control system which provides a regulated fluid flow rate regardless of the area rate of change of throttle valve metering orifice.

It is a further object of this invention to teach a fluid control system which regulates the rate of fluid flow through a throttle valve having a metering orifice defined by irregularly shaped ports so that the rate of flow is proportional to a selected control parameter which positions the throttle valve, in spite of variations in the rate of change of throttle valve orifice area for each increment of throttle valve position due to port irregularity.

It is a further object of this invention to teach control of the rate of flow through a throttle valve in a fluid control system, which throttle valve meters controlled fluid through matching ports, at least one of which is of irregular shape, by utilizing a shunt flow around the throttle valve and a reduced pressure drop thereacross when the orifice changes rapidly from a small to a large area.

It is a further object of this invention to control the pressure drop thru a throttle valve having a metering orifice defined by relatively movable, irregularly shaped ports, comprising simultaneously providing a bypass flow of fluid upstream of the diaphragm as a function of the pressure drop across the throttle valve and providing a shunt flow around the throttle valve.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a schematic representation of a preferred embodiment of our fluid control system.

Fig. 2 is a schematic representation of the throttle valve used in our fluid control system and illustrating the wall ports in the fixed and movable members thereof which coact to define the throttle valve metering orifice and which are movable relative to one another to vary the area of the orifice.

Fig. 3 is a graphic representation illustrating the rate of fluid flow through our control system and shows in phantom the type of fluid flow variations which would be encountered if an irregularly ported throttle valve were used with proper regulated pressure'drop across it but without the shunt flow provided by our invention.

Fig. 4 is a graphic representation of the weight flow of fluid through our fluid control system plotted against the throttle valve movable member. position or' control parameter valve to illustrate the fashion in which weight flow rate would vary if a throttle valve using a metering orifice defined by irregularly shaped ports were used with constant regulated pressure drop across it and without our invention.

Fig. 5 is a schematic representation of another'embodiment of our invention.

Fig. 6 is a schematic representation of still another embodimentof our invention.

Fig. 7 is a schematic representation of still another embodiment of our invention.

Fig. 8 is a fragmentary schematic representation of still another embodiment of our'invention.

Fig. 1 illustrates a preferred embodiment of our fluid control system 10 which is of the type taught in US. application Serial No. 611,339, filed September 21, 1956 by Thomas P. Farkas, and comprises a main duct system 12, through which the controlled fluid will flow, comprising upstream or fluid inlet end 14, downstream or fluid outlet end 16 and the connected ducting therebetween. Throttle valve 18 is located in the main duct system 12 between the upstream end 14 and the downstream end 16 thereof and meters the fluid passing therethru.

As best shown in Fig. 2, throttle valve 18 comprises fixed cylindrical sleeve member 20 and movable cylindrical sleeve member '22, which is coaxial with and bears against either the inner or outer surface of fixed sleeve 20. Fixed sleeve 20 has irregularly shaped wall port 24 therein which is shaped as joined small and large rectangular portions 26 and 28, respectively, while movable sleeve 22 contains rectangular wall port 30 which overlaps or aligns with stationary port 24 to define metering orifice 32 therewith. Port 30 is movable relative to port 24 so as to vary the area of metering orifice 32 as the relative positions of ports 24 and 30 change. While movable sleeve 22 of throttle valve 18 may be actuated by any desired control parameter or mechanism such as temperature and pressure ratio, for purposes of illustration it is shown to be actuatable as a function of a pressure parameter P Accordingly, the fluid to be controlled which enters inlet end 14 of the main duct system 12 of our fluid control system 10 establishing a main duct system throttle valve upstream pressure P upstream of throttle valve 18, is metered through orifice 32 of throttle valve 18 to establish a main duct system throttle valve pressure P downstream of throttle valve 18 from whence it is discharged through outlet end 16 of main duct system' l2.

Bypass line 40 communicates with main duct system 12 upstream of throttle valve 18 and contains bypass valve 42, which is positioned to regulate the amount of controlled fluid flow through bypass line 40. Bypass valve 42 comprises free floating pistons 44 and 46, which are separated by spring 48, and is subjected to pressure P; on one side thereof and to a reference or controlled pressure P which is introduced to reference pressure chamber 50 in a manner to be described hereinafter.

Chamber 60 is divided by flexible diaphragm 62 into two chambers, the first of which is in communication with main duct system 12 upstream of throttle valve 18 through line 64 to be subjected to pressure P the second of which is in communication with main duct system 12 downstream of throttle valve 18 through line 66 to be subjected to pressure P, so that diaphragm 62, which is biased by backup spring 68, is subjected to the pressure drop (P -P which exists across throttle valve 18 and therefore the position of diaphragm 62 is indicative of the pressure drop across throttle valve 18. Diaphragm 62 carries flapper 70 therewith to perform a function to be described hereinafter.

First duct means connects to reference pressure chamber 50 through line 82 and to fixed nozzle 84, which coacts with flapper 70 to form a variable area restriction 92, through line 86. Lines 82 and 86 join' line 88 which has fixed area restriction 90 therein. A reference pressure source P is introduced into first duct unit 80 to pass through fixed area restriction 90 and variable area restriction 92, formed by flapper 70 and nozzle 84, to establish Patented May 24.. 0

reference pressure P therebetween and deliver the reference pressure P into reference pressure chamber 50 to act against bypass valve 42 and coact with pressure P, in positioning bypass valve 42 to regulate the amount of controlled fluid flow through bypass line 40.

Second duct means 100 also communicates with line 86 and hence nozzle 84 and with reference pressure chamber 50 and is also is communication with reference pressure source P through duct 101, which has fixed area restriction 102 therein. Reference pressure poppet valve 104, which is biased open by spring 106, is located in second duct means 100 so that when poppet valve 104 is open reference pressure source P is in communication with nozzle 84 and reference pressure chamber 50 through both first duct means 80 and second duct means 100 but when poppet valve 104 is closed, reference pressure source P is in communication with nozzle 34 and reference pressure chamber 50 through first duct means 80 only.

A shunt line or duct 110 connects to main duct system 12 both upstream and downstream of throttle valve 18 to define a controlled fluid shunt passage around throttle valve 18. Shunt flow poppet valve 112 is positioned in shunt passage 110 so that when poppet valve 112 is closed no controlled fluid flows through shunt passage 110 but when poppet valve 112 is open, control fluid fiows around throttle valve 18 through shunt line 110. There may be installations where minimal shunt flow may be desired at all times and it may be desirable underthese circumstances to cause valve 112 to establish minimal flow when in its Fig. 1 position. This minimal flow may be valve 112 leakage flow.

Control parameter such as control pressure P which also actuates movable member 22 of throttle valve 18, is introduced through line 120 into annular chamber 122 to act against surface 124. Due to spring 106, poppet valve 104 is open and poppet valve 112, which is connected to poppet valve 104 through shaft 130, is closed when control parameter P is below a critical pressure and such that the reverse poppet valve condition occurs when control parameter P is above this critical pressure. The importance of the P critical pressure is that the critical pressure is reached when movable port 30 of throttle valve .18 moves from alignment with small rectangular portion 26 of fixed port 24 only, into alignment with large rectangular portion 28 and small rectangular portion 26 of fixed port 24 so that for a given increment of control pressure P change or movable sleeve 22 position, the rate of area change or orifice 32 changes drastically since said area is defined by the overlapping rectangular ports, at least one of which is of irregular shape.

Bypass valve 42, diaphragm 62, variable area restriction 92 and first and second duct means 80 and 100 serve to control the pressure drop (P -P across metering orifice 32 of throttle valve 18. Since the opposite sides of diaphragm 62 are subjected respectively, to main duct system throttle valve upstream and downstream pressures, flexible diaphragm is actuated and positioned as a function of pressure drop (P P across throttle valve 18 and serves to so position restriction 70 to regulate the area of variable area flapper 92. For the reasons more fully described in US. application Serial No. 663,491, filed June 4, 1957 by Thomas P. Farkas, reference pressure source P establishes reference pressure P to act against one side of bypass valve 42 and reference pressure P is a function of the area of flapper valve 92 and hence a function of the pressure drop (P -P across throtle valve 18. For purposes of explanation we may consider pressure P to be constant and it will readily be seen that when the pressure drop across throttle valve 18 exceeds the regulated value, P having increased to too great a pressure, diaphragm 62 will move flapper 70 to increase the area of variable area restriction 92 and hence reduce reference pressure P to cause bypassvalve 42 to open further and bypass a greater amount of controlled fluid through bypass line 40, thereby diminishing pressure P until it reaches the required value to reestablish the regulated pressure drop (P -P whereupon diaphragm 62, flapper 70 and bypass valve 42 will be re-established at an equilibrium position to maintain the desired pressure drop. Had the P pressure reduced in value to diminish the pressure drop (P -P below the regulated value, flexible diaphragm 62 would actuate flapper 70 to reduce the area of variable area restriction 92 and increase reference pressure P to move bypass valve 42 toward a closed position, thereby reducing the flow of controlled fluid through bypass line 40 to increase pressure P to the necessary value to re-establish the regulated throttle valve pressure drop (P -P Fluid flow control system 10 would be able to control the pressure drop across throttle valve 18 in the fashion just described without further implementation if it were not for the fact that at least one of the wall ports, 24 and 30, in throttle valve 18 is irregular in shape.

Referring to Fig. 2 let us consider that movable wall port 30 of movable sleeve 22, which is actuated by any controlled parameter and is illustrated to be actuated by control pressure P first comes into alignment with fixed wall port 24 at point A. At point B, movable port 30 comes into alignment with the large rectangular portion 28 of port 24 while continuing in alignment with the small rectangular portion 26 thereof and continues in alignment with both the large rectangular portion 28 and the small rectangular portion 26 to point C. Fig. 2 illustrates throttle valve metering orifice 32 as being defined by wall ports 30 and 24 and being a rectangular orifice with dimensions X and Y so that the area of throttle valve orifice 32 illustrated in Fig. 2 may be cal culated by the product XY. It is well known in the hydraulic field that the rate of flow through a metering orifice is proportional to the area of the orifice when the pressure drop across the orifice is maintained constant and this principle is used in our fluid flow control system 19 to regulate the rate of controlled fluid flow through throttle valve metering orifice 32 as a function of the controlled parameter P by regulating the area of orifice 32 as a function of parameter P while maintaining the pressure drop across orifice 3'2 constant. Continuing with our description of Fig. 2, area XY of orifice 32 will increase proportionally for each particular increment of movement of movable port 30 since orifice dimension Y will remain constant and each particular increment movement of movable port 30 will be reflected directly in the dimension X of orifice 32 and hence in the area of orifice 32 and this condition will exist between points A and B. Between points A and B, movable port 30 overlaps small rectangular portion 26 of fixed port 24 and coacts therewith to define a rectangular metering orifice 32 over a range of small areas. Once movable port 30 reaches point B, the next increment thereof toward point C will greatly increase the area of metering orifice 32 since movable port 32 will come into alignment with both the small rectangular portion 26 and the large rectangular portion 28 of fixed port 24. From points B to C, ports 30 and 24 coact to define a metering orifice over a range of large areas.

Referring to Fig. 4 it will be noted that the rate of flow or weight flow of the controlled fluid passing through throttle valve orifice 32 will increase at a uniform rate proportional to the position of the throttle valve and the value of P between throttle valve positions A and B and that the rate of flow or weight flow will increase at a greater rate between throttle valve positions and P values B and C. This is contrary to the desired objective of control system 10, which as stated supra, is to regulate the rate of controlled fluid flow in proportion to the value of the control parameter P which is used herein to determine throttle valve position. Since the pressure drop across orifice 32 affects the-rate of flow therethrough, we might reduce the pressure drop across orifice 32 when we pass beyond position B..toward position C so that the throttle valve orifice area and pressure drop will bear the same relation to one another and hence give a controlled fluid flow rate proportional to throttle valve position and hence proportional to control parameter P whether movable port 30 is between points A and B or between points B and C.. We would find, however, as best shown in Fig. 3, that if wemerely reduced the pressure drop across orifice 32 in passing through point B toward point C, we would be able to maintain the controlled flow rate through orifice 32 equal on opposite sides of point B but, a sudden drop in the absolute value of the controlled fluid flow rate, W would be encountered at point B before our control system 10 could be established to effect the desired rate flow coordination. Accordingly, if we merely reduce the pressure drop across orifice 32 when port 30 passes through point B toward point C our controlled fluid flow rate W would change from point 1 at valve position A to point 2 at valve position B before throttle valve pressure drop decrease, to point 3 at valve position B after throttle valve pressure drop decrease and thence along the desired rate line to point 4 as throttle valve position C is approached.

To overcome the difliculty just described, applicants provide shunt flow around throttle valve 18 simultaneously with throttle valve pressure drop reduction at point B so that controlled fluid flow rate W will move from point 1 in Fig. 3 to'point 2 in Fig. 3 and, due to the combined and simultaneous action of shunt flow and throttle valve orifice pressure'drop reduction at point B, will continue along the same rate line to point 5 at throttle valve position C. In this fashion the objective of regulating fluid flow rate through throttle valve 18 proportional to control parameter P has been accomplished even though throttle valve orifice 32 is defined by irregularly shaped window type aligned and overlapping ports 24 and 30.

Operation To see how the aforementioned simultaneous shunt flow and throttle valve orifice pressure drop reduction is accomplished, let us again refer to Fig. 1. As previously described, reference pressure poppet valve 104 is connected to shunt flow poppet valve 112 through shaft 130 and spring 106 biases reference pressure poppet valve 104 open and shunt flow flow poppet valve 112 closed. when controlparameter P which acts through line 120 and annulus 122 against surface 124, is below a predetermined value and this predetermined value is specifically selected to be the value at which control parameter P causes throttle valve movable port 30 to move past throttle valve point B toward throttle valve point C (Figs. 2-4). When control parameter P exceeds this predetermined point B value, spring 106 is overcome and reference pressure poppet valve 104 closes while shunt flow poppet valve 112 opens.

Consider first the operation of our fluid flow control system when poppet valves 104 and 112 are in their Fig. 1 position. The control fluid which passes through throttle valve orifice 32 establishes a pressure drop (P -P thereacross, which pressure drop, in the fashion described previously, is regulated by the position of flexible diaphragm 62 and flapper 70 to establish a first reference pressure P which positions bypass valve 42 to cause the proper amount of controlled fluid flow through bypass line 40 to regulate pressure drop (P -P It will be noted that in the Fig. 1 position shunt flow poppet valve 112 is closed, and there is no controlled fluid flow through shunt line 110, further, that with reference pressure poppet valve 104 open reference pressure P can pass to reference pressure chamber 50 and variable area restriction 92 through both first duct means 80 and second duct means 100 thereby establishing a first reference pressure P to position bypass valve 42 and to regulate the pressure drop (P -P across throttle valve orifice 32 in the fashion described supra.

7 When control parameter P reaches the selected valu at which movable port 30 passes through point B toward point C (Figs. 2-4), spring 106 is overcome and reference pressure'poppet valve 104 is closed and shunt poppet valve 112 is opened. With the poppet valves 104 and 112 in their shifted positions, controlled fluid flows through shunt line 110 and fluid at reference pressure P from reference source pressure P may pass into chamber 50 and variable area restriction 92 through first duct means only, since second duct means is now blocked by poppet valve 104. This causes a reduction in the reference pressure P in chamber 50 to cause bypass valve 42 to open thereby bypassing a greater amount of controlled fluid to coactwith the action of shunt flow to reduce pressure P thereby reducing the pressure drop across throttle valve orifice 32 to a new'value (P1I--Py), whereupon variablearea restriction 92 reduces in area to establish a new reference pressure within chamber 50; The change of force of the spring 68 attendant to this restriction 92 area change results in a reduced pressure drop (P -P across the throttle valve orifice 32.

In this fashion the rate of flow of controlled fluid through 1 throttle valve metering orifice 32 is maintained proportional to the value of the control parameter P to obtain the result illustrated graphically by solid line in Fig. 3.

A second embodiment of our invention is shown in Fig. 5 in which reference pressure poppet valve 104' is placed in contact with spring 68 and the position of shunt flow poppet valve 112 is unchanged from its Fig. 1 position so that when control parameter P reaches its critical pressure wherein it moves movable port 30 from the throttle valve A to B position range into the throttle valve B to C position range shunt poppet valve 112 is opened to permit shunt flow through line while throttle valve 104' is actuated to reduce the pressure on spring 68', therebypermitting diaphragm 62' to actuate flapper 70 to increase the area of variable area restriction 92" thereby reducing the reference pressure P in control pressure chamber 50' to cause bypassvalve 42 to increase area and bypass more controlled fluid through bypass line 40' hence reducing the pressure drop across throttle valve 18' simultaneously with inaugurating of shunt flow therearound. The same effect can be accomplished by mechanically linking piston 104 to the shunt flow poppet valve 112' as shown in Fig. 8. For pur-.

poses of clarity, additional reference numerals have been added to Fig. '5 to indicate the comparable parts illustrated in Fig. 1 such that for comparable parts Fig. 1 carries the reference numeral only while Fig.- 5 carries the reference numeral primed, for example in Fig. 1 the fluid flow control system is designated as 10 whereas in Fig. 5 it is designated at 10. used in identifying comparable parts in Figs.- 6 and 7 with a double prime used with the reference numerals in Fig. 6 and triple prime with the reference numerals used in Fig. 7.

Referring to Fig. 6 We see another embodiment of our invention in which the position of shunt flow poppet valve 112" is unchanged from the Fig. 1 position but in which reference pressure poppet valve 104" is positioned in line 66" to regulate the size of a variable area orifice therein. In Fig. 6, when the control parameter P passes through the throttle valve point B critical pressure, shunt throttle valve 112" is caused to open to inaugurate shunt flow through line 110" while reference pressure poppet valve 104" is caused to open also. The normal quiescent fluid flow passing through the flapper valve 70" creates a pressure drop across the restriction introduced by 104". When this restriction is removed the pressure drop ceases and the result is to cause dia-' phragm 62" to move flapper 70" in a direction to increase the area of variable area flapper valve 92" thereby reducing the reference pressure P in chamber 50'? tov Similar methods will be open bypass valve 42" to bypass-a greater amount of controlled fluid through bypass line 42" thereby reducing the pressure drop across throttle valve 18" simultaneously with the inauguration of shunt line flow. The same effect can be accomplished by mechanically linking piston 104" to the shunt flow poppet valve 112" as generally shown in Fig. 8.

Referring to Fig. 7 we see another embodiment of our invention in which the position of shunt flow poppet valve 112' is unchanged from the Fig. l configuration but a shunt line 150 with fixed restriction 152 therein connects bypass line 40" with the volume 154 defined between pistons 44" and 46" of bypass valve 42" and a second line 156, with reference pressure poppet valve 104" constituting a variable area orifice therein, connects chamher 154 to drain. With this configuration, when the control parameter P reaches the previously described critical point B, shunt poppet valve 112" opens to inaugurate flow through shunt line 110' and reference pressure poppet valve 104 is actuated to reduce the size of variable area orifice 160 in line 150, thereby increasing the pressure within chamber 154 to move bypass valve 42" to an increased area position, thereby increasing controlled fluid bypass flow to reduce pressure drop across throttle valve 18" simultaneously with the inauguration of shunt flow through line 110". The force balance on the piston 46" is changed by the loss of pressure in chamber 154. This requires a change in area of the flapper 92" to eflect the necessary change in controlled pressure in chamber 50". The spring force change attendant to the flapper area change resets the regulated pressure (P P to the desired new level. The piston 160 may be linked mechanically to the shunt flow poppet valve 112" to produce the same effect.

It is to be understood that our invention is not limited to the specific embodiment herein illustrated and described but may be used in other ways without departure from its spirit as defined by the following claims.

We claim:

1. In a fluid flow control system, a throttle valve having an orifice through which the fluid must pass which orifice has two distinct area ranges, means to regulate the pressure drop across said throttle valve, and means controlling said pressure drop regulating means to vary said pressure drop across said throttle valve as said orifice changes from one of said area ranges to the other of said area ranges.

2. In a fluid flow control system, a throttle valve comprising relatively movable members having overlapping ports defining an orifice through which the fluid passing through said throttle valve is metered, at least one of said ports being of irregular shape including a small area region and a large area region so that said overlapping ports define a metering orifice which may be varied thru a range of large areas and a range of small areas, means to regulate the pressure drop across said throttle valve when said orifice is in either of said area ranges, .and means to control the fluid flow rate through said system to be proportional to the relative position of said throttle valve ported members.

3. In a fluid flow control system, a throttle valve actuatable to define an orifice through which the fluid must pass which orifice has a range of small areas and range of large areas, means to regulate the pressure drop across said throttle valve, duct means defining shunt flow around said throttle valve, and means to simultaneously actuate said pressure drop regulating means to decrease said pressure drop across said throttle valve and increase fluid flow through said duct means as said orifice changes from said range of small areas to said range of large areas to cause the fiuid flow rate through said throttle valve to remain constant.

4. in a fluid flow control system, a throttle valve comprising a fixed cylindrical sleeve having a wall port therein defining joined small and large rectangles and a movable cylindrical sleeve concentric and in sliding contact with said fixed sleeve and having a wall port defining a rectangle, means to actuate said movable sleeve to bring said wall ports into alignment to define an orifice through which the fluid passing through said throttle valve is metered, which orifice is varied through a range of small areas when said actuating means aligns said movable sleeve port with said small rectangle portion of said fixed sleeve port and through a range of large areas when said actuating means aligns said movable sleeve port with said large rectangle portion of said fixed sleeve port, means to regulate the pressure drop across said throttle valve when said orifice is in either of said area ranges, and means to control the fluid flow rate through said system to be proportional to the position of said movable sleeve.

5. In a fluid flow control system, a throttle valve comprising a fixed cylindrical sleeve having a wall port therein defining joined small and large rectangles and a movable cylindrical sleeve concentric and in sliding contact with said fixed sleeve and having a wall port defining a rectangle, means to actuate said movable sleeve to bring said wall ports into alignment to define an orifice through which the fluid passing through said throttle valve is metered, which orifice is varied through a range of small areas when said actuating means aligns said movable sleeve port with said small rectangle portion of said fixed sleeve port and through a range of large areas when said actuating means aligns said movable sleeve port with said large rectangle portion of said fixed sleeve port, means to regulate the pressure drop across said throttle valve when said orifice is in either of said area ranges, duct means defining shunt flow around said throttle valve, and means to simultaneously actuate said pressure drop regulating means to decrease said pressure drop across said throttle valve and increase fluid flow through said duct means as said orifice changes from said range of small areas to said range of large areas to cause the fluid flow rate through said throttle valve to be proportional to the position of said movable sleeve.

6. In a fluid flow system for controlling the flow of a fluid having a main duct system through which the controlled fluid passes, a throttle valve in said main duct system comprising a fixed cylindrical sleeve having a wall port therein defining joined small and large rectangles and further comprising a movable cylindrical sleeve concentric and in sliding contact with said fixed sleeve and having a wall port therein defining a rectangle, means to actuate said movable sleeve to bring said wall ports into alignment to define an orifice through which the controlled fluid passing through said main duct system is metered, which orifice is varied through a range of small areas when said actuating means aligns said movable sleeve port with said small rectangle portion of said fixed sleeve port and through a range of large areas when said actuating means aligns said movable sleeve port with said large and small rectangle portions of said fixed sleeve port, a chamber divided by a spring loaded flexible diaphragm and communicating with said main duct system both upstream and downstream of said throttle valve to subject one side of said diaphragm to main duct system throttle valve upstream pressure and the other side of 'said diaphragm to main duct system throttle valve downstream pressure, a flapper carried by said diaphragm, a fixed nozzle positioned adjacent said flapper and defining a variable area restriction therewith as said flapper moves with said diaphragm, a bypass line connected to said main duct system upstream of said throttle valve and having a pressure actuated bypass valve with first and second sides therein to regulate the controlled fluid flow therethrough which bypass valve is subjected on said first side to said main duct system throttle valve upstream pressure, first duct means including a reference pressure chamber communicating with said second side of said "bypass" valve and connected to said nozzle and having a fixed restriction therein, a reference pressure source introducing pressurized fluid to said first duct means to establish a reference pressure between said fixed orifice and variable area restriction which reference pressure is proportional to the area of said variable area restriction and which reference pressure is introduced to said reference pressure chamber to act upon said second side of said bypass valve, second duct means with a fixed orifice therein connected to said nozzle and said reference pressure chamber and also subjected to said reference pressure source, a reference pressure poppet valve located in said second duct means so that fluid from said reference pressure source may flow to said nozzle and said reference pressure chamber through both said first and second duct means when said reference pressure poppet valve is open, third duct means connected to said main duct system: both upstream and downstream of said throttle valve and defining a shunt flow passage around said throttle valve, a shunt flow poppet valve located in said third duct means so that no controlled fluid passes through said third duct means when said shunt flow poppet valve is closed, means to bias said shunt flow poppet valve closed and said reference pressure poppet valve open so that a first reference pressure communicates with said reference pressure chamber to coact with said main duct system throttle valve upstream pressure to position said bypass valve to control the controlled fluid pressure difference upstream and downstream of said throttle valve, and means to open said shunt flow poppet valve and close said reference pressure poppet valve when said movable sleeve wall port moves from alignment with said fixed sleeve wall port small rectangle portion into alignment with said fixed sleeve wall port large and small rectangle portions to institute controlled fluid flow through said shunt flow passage and to stop fluid flow from said reference pressure source through said second duct means thereby reducing said first reference pressure to a second reference pressure and reposition said bypass valve to permit greater controlled fluid flow through said bypass line to reduce and control the controlled fluid pressure difference upstream and downstream of said throttle valve.

7. In a fluid flow system for controlling the flow of a fluid having a main duct system through which the controlled fluid passes, a throttle valve in said main duct system comprising a fixed cylindrical sleeve having a wall port therein defining joined small and large rectangles and further comprising a movable cylindrical sleeve concentric and in sliding contact with said fixed sleeve and having a wall port therein defining a rectangle, means responsive to an actuating pressure to actuate said movable sleeve as a function of said actuating pressure to bring said wall ports into alignmentto define'an orifice through which the controlled fluid passing through said main duct system is metered, which orifice is varied through a range of small areas when said actuating means aligns said movable sleeve port with said small rectangle portion of said fixed sleeve port and through a range of large areas when said actuating means aligns said movable sleeve port with said large and small rectangle portions of said fixed sleeve port and which orifice changes from said range of small areas to said range of large areas when said actuating pressure is at critical value, a chamber divided by a spring loaded flexible diaphragm and communicating with said main duct system both upstream and downstream of said throttle valve to subject one side of said diaphragm to main duct system throttle valve upstream pressure and the other side of said diaphragm to main duct system throttle valve downstream pressure, a flapper carried by said diaphragm, a fixed nozzle positioned adjacent said flapper and defining a variable area restriction therewith as said flapper moves with said diaphragm, a bypass line connected to said it) main duct system upstream of said throttle valve and having a pressure actuated bypass valve with first and second sides therein to regulate the controlled fluid flow therethrough which bypass valve is subjected on said first side to said main duct system throttle valve upstream pressure, first duct means including a reference pressure chamber communicating with said second side of said bypass valve and connected to said nozzle and having a fixed restriction therein, a reference pressure source introducing pressurized fluid to said first duct means to establish a reference pressure between said fixed orifice and variable area flapper valve which reference pressure is proportional to the area of said variable area restriction and which reference pressure is introduced to said reference pressure chamber to act upon said second side of said bypass valve, second duct means with a fixed orifice therein connected to said nozzle and said reference pressure chamber and also subjected to said reference pressure source, a reference pressure poppet valve located in said second duct means so that fluid from said reference pressure source may flow to said nozzle and said reference pressure chamber through both said first and second duct means when said reference pressure poppet valve is open, third duct means connected to said main duct system both upstream and downstream of said throttle valve and defining a shunt flow passage around said throttle valve, a shunt flow poppet valve located in said third duct means so that no controlled fluid passes through said third duct means when said shunt flow poppet valve is closed, means to bias said shunt flow poppet valve closed and said reference pressure poppet valve open when said actuating pressure is below said critical value so that a first reference pressure communicates with said reference pressure chamber to coact with said main duct system throttle valve upstream pressure to position said bypass valve to control the controlled fluid pressure difference upstream and downstream of said throttle valve so that the rate of controlled fluid flow thru said system is proportional to said movable sleeve, and means responsive to said actuating pressure to simultaneously open said shunt flow poppet valve and close said reference pressure poppet valve when said actuating pressure is at said critical value to institute controlled fluid flow through said shunt flow passage and to stop fluid flow from said reference pressure source through said second duct means thereby reducing said first reference pressure to a second reference pressure and reposition said bypass valve to permit greater controlled fiuid flow through said bypass line to reduce and control the controlled fluid pressure difference upstream and downstream of said throttle valve so that the rate of controlled fluid flow thru said system continues to be proportional to the position of said movable sleeve.

8. In a fluid flow control system, a throttle valve comprising relatively movable members having overlapping ports defining an orifice through which the fluid passing through said throttle valve is metered, at least one of said ports being of irregular shape including a small area region and a large area region so that said overlapping ports define a metering orifice which may be varied thru a range of large areas and a range of small areas, means to establish a reference pressure proportional to the pressure drop across said orifice and to bypass fluid from said system upstream of said throttle valve, means to regulate the pressure drop across said throttle valve when said orifice is in either of said area ranges, and means to establish a new reference pressure when said orifice area changes from one of said ranges to the other to control the fluid flow rate through said system to be proportional to the relative position of said throttle valve ported members.

No references cited. 

